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Cryptic "Garbage" Cell Turns Out To Be New Type Of Stem Cell


Robin Andrews

Science & Policy Writer

311 Cryptic "Garbage" Cell Turns Out To Be New Type Of Stem Cell
Stem cells are seen as a central pillar of regenerative medicine. Juan Gaertner/Shutterstock

Pluripotent stem cells are heavily sought after by medical researchers who see them as a game-changer. With the ability to regenerate damaged tissue, including that found in the heart, brain, and pancreas, this perception may not be overblown.

Now, a team of researchers have stumbled across a new type of stem cell. As the study in the journal Stem Cell Reports reveals, these “iXEN” stem cells were once thought to be potentially dangerous byproducts of other developing stem cells. In fact, they may prove to be far more useful than harmful.


When it comes to stem cells, researchers generally experiment with three types. Embryonic stem cells come from fertilized eggs discarded from in vitro fertilization (IVF) operations. Adult stem cells are found in other tissues, and are designed to replace damaged cells. “Induced” pluripotent stem cells (iPSCs) are forged from developed cells that have been reprogrammed to become more primitive.

iPSCs can not only develop into almost any type of cell in the body, but they can also replicate themselves indefinitely, meaning that they can potentially provide someone with a source of unlimited cell types. In the process of producing iPSCs, however, thousands of other peculiar and poorly understood cells are also generated. iXEN cells, which stands for induced extraembryonic endoderm stem cells, are one such example.

During the development of an embryo, naturally occurring XENs grow alongside pluripotent stem cells. Scientists discovered that these XENs turned into tissues that formed outside of the embryo itself.

These newly discovered induced stem cells were once thought to be cancer-like. Matej Kastelic/Shutterstock


iXEN cells also spontaneously grow alongside iPSCs, but unlike their XEN counterparts, these were thought to be dangerous, perhaps even cancerous. Careful observation of developing iXEN cells by the team at Michigan State University (MSU) revealed that they aren’t cancerous at all, but in fact a new type of stem cell.

During the production of iPSCs, the researchers decided to change the way the iXEN cells behave by altering how their genes “express” themselves. By inhibiting this genetic expression, they found that the production of additional iXEN cells decreased, while the production of iPSCs increased.

Theoretically, the team have found a mechanism wherein far more iPSCs can be produced than ever before. All of these cells could potentially go on to be used to regenerate damaged tissue, so the more there are at the end of the process, the better.

“Other scientists may have seen these cells before, but they were considered to be defective, or cancer-like,” said Tony Parenti, a molecular biologist at MSU and the lead author of the study, in a statement. “Rather than ignore these cells that have been mislabeled as waste byproducts, we found gold in the garbage.”


These XEN and iXEN cells were cultured from mice, and both have yet to be discovered or derived from humans. The search for these novel stem cells in people has just begun.

iXENs aren’t the only new stem cell type officially discovered this month. Just this week, it was announced that “naïve” pluripotent stem cells were produced from human embryos for the first time in history. These cells are not primed to become any set specialized cell type, and are incredibly easy to program to change into any cell type the researchers wish.


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